A back muscle saves the pianist's career

Surely whoever wrote the article is not a pianist, but reading

"Four months later, playing and suffering, Janina could already perform a repertoire from the 1700s.

Another month and she had already started with Chopin."

Reading it, it almost seems as if there is a scale of difficulty linked to the axis of time... I was wondering if it can actually be like that... surely Chopin requires a well-functioning limb, but I would say the same for Bach and obviously many others...